DE646274C - Circuit for direct current railways with series motors - Google Patents

Description

Circuit for direct current railways with series motors The present The invention relates to circuits for direct current railways with series motors, especially those in which the motor field windings in the case of regenerative braking connected to the mains via a series resistor (Fig. z). As the field winding of a series motor has only a relatively low resistance In regenerative braking circuits of this type, most of the excitation power is in the series resistor W lost. In the case of multi-engine vehicle equipment, this disadvantage can be caused by series connection several motor field windings can be reduced. Even then, it remains as a result of the large series resistance losses is the ratio between that drawn from the network The excitation power and the anchor power returned to the network are unfavorable in comparison with other current recovery circuits for series motors where lower Excitation losses occur, e.g. B. those with shunt compound winding or converter for indirect supply of the motor field winding.

According to the invention, the efficiency of current recovery circuits with series motors whose field windings have a series resistor from Mains are fed, improved by the fact that the motor field windings in the driving circuit Resistors are connected in parallel, which in regenerative braking wholly or partially are to be switched off. The number of turns of the field windings is compared to normal motors significantly increased, so that a low excitation current is sufficient and therefore during regenerative braking the motor field winding can be preceded by a high resistance; therefore be the losses in the field circuit during regenerative braking are greatly reduced. To while driving If the field strength is not too high, the motor field winding becomes a resistor in parallel switched, which causes a relatively small additional loss. The invention is based on the knowledge that from the described change in the motor field winding resulting deterioration in electromechanical efficiency when driving exerts a significantly smaller influence on the total power consumption than that at the same time resulting electrical efficiency improvement in regenerative braking, so that overall an improved watt-hour consumption per tonne-kilometer results.

It has become known for engine controls after they have been switched off the armature resistance increases the speed by weakening the field bring about. The field is completely normal Cascading field and so dimensioned that there is a considerable series resistance and requires a high excitation current. However, this should be done precisely for reasons of animal welfare avoided by the invention. An arrangement is also known at the parallel to the series-connected field windings of DC series motors a resistor is connected in parallel, which is disconnected during regenerative braking will. However, this circuit lacks the inventive feature, namely that too the fields are weakened while driving. In addition, the arrangement is merely the task is based on overloading the field windings during short-circuit purification to behave. When short-circuit braking, the field windings must be in the known Special circuit take up a multiple armature current. To avoid this, will a relief resistor switched on.

Finally, a switching arrangement has become known with the it is true that the same is partly achieved with respect to the 1, Iotorcharacteristic as by the subject of the invention, with which, however, the motor fields ini utzbremsbetrieb, d. H. with series connection of the partial windings only take over half the current as with Driving operation where both parts are connected in parallel. Besides this ratio i : 2 with regard to the current consumption of the field windings, there are other subdivisions possible, with which, however, only very specific proportions, such as. B. i: 3, i: 4, etc., can be produced. However, this fact means that one has to do with the choice of the field current ratio in the case of emergency and driving or short-circuit braking operation is bound to very specific numerical values. In the circuit according to the invention on the other hand, there is complete freedom in the choice of the specified current ratio. Anyone skilled in the art knows, however, that the correct size of the current ratio for the efficiency the `#braking is of the utmost importance. Mine exact consideration of this current ratio but is not possible with the means of the known arrangement.

Fig. 2 shows an embodiment of the circuit according to the invention for a single-engine railcar equipment. 5 'is a shunt resistor, which in the driving circuit shown is parallel to the motor field winding H and is switched off with the Nutzbreiliseti according to the circuit in Fig. i.

With the new circuit «earth the field windings of the motors in such a way that that despite the parallel connection of the mentioned resistance S generate sufficient magnetic flux. So that this condition also applies to existing ones "The railcar is met, the fair power recovery converted after the new circuit “If you want to earth, the field windings of your motors must be used against those with a larger number of turns be replaced with a correspondingly increased resistance. By appropriate dimensioning the resistance S (Fig. 2), which is connected in parallel when driving, can be achieved that a motor modified in the manner described will have the same tractive force characteristic curve when driving as before your university building.

The favorable overall efficiency of the new circuit should be at one simple numerical example for a single-engine railcar equipment in circuit shown in Fig. i and 2.

The motor under consideration is wound for 55o V and has an hourly current of 7o anil>. This corresponds to a power consumption of 38.5 k`N '. The original resistance of the field winding is 0.2 ohms. If the motor is then on when driving in the circuit shown in Fig. 2, the l = R losses for the hourly current in the field winding are calculated to be 4900 X 0.2 or 98o watts; the losses are therefore around 2.5 % of the total electrical power consumed by the motor. If one now assumes that the field windings of the motor are replaced by other rolling .1 times the number of windings with the same external dimensions, the field resistance is so great that it is 3.2 ohms. So that the new field windings produce the same magnetic flux as the original one, the excitation current may amount to a quarter of the total current. The required closing resistance S is easy to calculate. A1sTotal resistance of field winding and shunt resistance results in 0.8 ohms, i.e. four times the value of the original field resistance. This means that the excitation losses when driving are four times greater and amount to 10% of the engine power consumed.

In the case of the utzbrinsen according to Fig. I, after the change, there is the .ifaclie `@ 'number available for field magnetization. Therefore, a quarter of the excitation current originally taken from the network to the same number of ampere-turns to generate magnetization of the field poles. The pathogen losses also go accordingly back to the fourth part. The assumed single-engine vehicle equipment is fair so opposite each other: Increase in excitation losses while driving: 1o -a, 5 = 7.5% of the electrical power consumed by the motor.

Reduction of the excitation losses during regenerative burning: 1 - '/ 4 = 750/0 des original value.

In Figs. 3 to 6 is the electrical when driving or returned Power shown for the single-engine railcar under consideration.

Fig.3 contains the power consumption and the excitation losses at Driving depending on the speed before the motor in the described Way is changed, and Fig. 4 the same curves after the change. The overall performance runs the same in both cases, while the excitation losses in Fig. 4, as through Hatching is highlighted, are enlarged to an insignificant extent.

Figure 5 contains the corresponding performance curves for regenerative braking before the change and Fig.6 those after the engine change. In both In some cases, the power delivered to the grid is denoted by -N and plotted upwards. It represents the difference between the - (- N designated, plotted downwards Excitation power and the returned armature power applied upwards. For the sake of simplicity, it is assumed that the armature current from the onset of braking remains unchanged up to a certain minimum speed. Consequently the required excitation power increases within the considered speed range according to the straight line drawn. The corresponding performance curves are shown in Fig.6 shown for the modified motor with field windings with a higher number of turns. the Excitation power is significantly lower here, so that the corresponding straight line is flatter runs as in Fig. 5. The difference between that in the new circuit and before changing the motor back into the network is shown in Fig.6 Hatching highlighted. A comparison of the two hatched areas in Fig. 4 and 6 clearly show that the increase in the recovered power is the additional losses occurring when driving outweighs by far, so that the overall efficiency is significantly improved.

The above example of a single engine vehicle was chosen to show the essence of the new circuit particularly clearly. With multiple engines Vehicles is the difference between increased driving loss and decreased loss smaller when braking, since with regenerative braking all fields are usually connected in series so that the entire required excitation power of that of an individual Engine. But the new gearshift is also useful in vehicles with many engines a substantial improvement, and it can also be used with great efficiencies the power recovery can be achieved, as it is otherwise only with compound or series motors, which are excited by converters can be achieved.

When driving after starting the engine, the motor field becomes more familiar Way to increase the speed by additional shunt resistors weakened, which are marked with O in Fig. a, then on average increases over a trip between two stops of the one shown in Fig. d. and 6 shown by hatching Difference between the increase in excitation losses while driving and their decrease with the pulp even further.

In many vehicles with emergency braking operation, the Short-circuit braking used, for example as emergency braking. The motor circuit according to the present invention can be readily applied to vehicles of this type use. The field weakening resistance S remains exactly as in the driving circuit connected in parallel during the short-circuit burning of the motor field winding.

Also in combined short-circuit and regenerative braking circuits, in which pure short-circuit braking is used until the motor voltage reaches the Mains voltage predominates, the invention can be used without further ado. It will then a switching device is provided in a known manner, which automatically in Depending on the voltage of the traction motors, the brake circuit is connected to the mains. From then on, both short-circuit and regenerative braking take place. Also in this The resistance S of the motor field winding can occur during pure short-circuit braking remain connected in parallel.

Towards the end of the short-circuit braking, the resistance can be completely or partially switch off, so that a desired increase in braking effect shortly before The vehicle comes to a standstill.

Claims (2)

PATENT CLAIMS: i. Circuit for direct current railways with series motors, characterized in that the motor field windings with opposite conventional series motors essential, e.g. B. four times higher Number of turns, executed and while driving and possibly also during short-circuit burning (lurking are connected in the 2, # level circuit to resistors lying in the armature circuit, which lead the main part of the armature current and during regenerative braking in whole or in part be separated. 2. A circuit according to claim i, characterized in that the @ 1-motor field windings during the burnout via a series resistor to which: Fetz are connected.